U.S. patent number 7,063,153 [Application Number 10/773,632] was granted by the patent office on 2006-06-20 for methods and compositions for cementing wells.
Invention is credited to Larry S. Eoff, Krista L. Keener.
United States Patent |
7,063,153 |
Eoff , et al. |
June 20, 2006 |
Methods and compositions for cementing wells
Abstract
Methods of cementing subterranean zones penetrated by well bores
and well cement compositions. A well cement composition of the
invention basically comprises a hydraulic cement, water in an
amount sufficient to form a pumpable slurry and a fluid loss
control polymer additive comprising 77.9 weight % of the calcium
salt of 2-acrylamido-2-methyl propane sulfonic acid, 8 weight % of
the calcium salt of maleic acid, 11 weight % of N-vinyl
caprolactam, 3 weight % of 4-hydroxybutyl vinyl ether and 0.1
weight % of methylene bisacrylamide.
Inventors: |
Eoff; Larry S. (Duncan, OK),
Keener; Krista L. (Duncan, OK) |
Family
ID: |
34886524 |
Appl.
No.: |
10/773,632 |
Filed: |
February 6, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040159431 A1 |
Aug 19, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10176344 |
Jun 20, 2002 |
6715552 |
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Current U.S.
Class: |
166/293; 106/808;
166/295; 523/130 |
Current CPC
Class: |
C04B
24/163 (20130101); C04B 24/2629 (20130101); C04B
24/2652 (20130101); C04B 24/2688 (20130101); C04B
28/02 (20130101); C04B 28/04 (20130101); C09K
8/46 (20130101); C09K 8/487 (20130101); C04B
28/04 (20130101); C04B 22/0026 (20130101); C04B
28/04 (20130101); C04B 22/0026 (20130101); C04B
24/163 (20130101); C04B 28/02 (20130101); C04B
24/2688 (20130101); C04B 24/163 (20130101); C04B
24/2629 (20130101); C04B 24/2652 (20130101); C04B
24/2688 (20130101); C04B 2111/00146 (20130101); C04B
2103/46 (20130101); C04B 2103/46 (20130101); C04B
2103/46 (20130101); C04B 2103/46 (20130101); C04B
2103/46 (20130101) |
Current International
Class: |
E21B
33/13 (20060101) |
Field of
Search: |
;166/293,295 ;523/130
;106/808 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 375 818 |
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Jan 2004 |
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EP |
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2 210 888 |
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Jun 1989 |
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GB |
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WO 99/26991 |
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Jun 1999 |
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WO |
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WO 03/085013 |
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Oct 2003 |
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WO |
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WO 03/97721 |
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Nov 2003 |
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WO |
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Other References
PTO-04-4736 translation of WO 03/085013 A2, translated Aug. 2004 by
Ralph McElroy Translation Company, 25 pages. cited by examiner
.
Foreign communication from a related counterpart application dated
May 3, 2005. cited by other.
|
Primary Examiner: Mitchell; Katherine
Attorney, Agent or Firm: Roddy; Craig W. McAfee &
Taft
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a Continuation-In-Part of U.S. patent
application Ser. No. 10/176,344 filed on Jun. 20, 2002 now U.S.
Pat. No. 6,715,552, the entire disclosure of which is incorporated
herein by reference.
Claims
What is claimed is:
1. A method of cementing a subterranean zone penetrated by a well
bore comprising the steps of: (a) preparing or providing a cement
composition comprising a hydraulic cement, sufficient water to form
a pumpable slurry and a fluid loss control polymer additive
comprising 77.9 weight % of the calcium salt of
2-acrylamido-2-methyl propane sulfonic acid, 8 weight % of the
calcium salt of maleic acid, 11 weight % of N-vinyl caprolactam, 3
weight % of 4-hydroxybutyl vinyl ether and 0.1 weight % of
methylene bisacrylamide; (b) placing said composition in said
subterranean zone to be cemented; and (c) allowing said cement
composition to set into an impermeable solid mass therein.
2. The method of claim 1 wherein said fluid loss control polymer
additive is present in said cement composition in an amount in the
range of from about 0.1% to about 2% by weight of cement
therein.
3. The method of claim 1 wherein said hydraulic cement in said
cement composition is selected from the group consisting of
Portland cements, pozzolana cements, gypsum cements, aluminous
cements and silica cements.
4. The method of claim 1 wherein said hydraulic cement is Portland
cement.
5. The method of claim 1 wherein said water in said cement
composition is selected from the group consisting of fresh water
and salt water.
6. The method of claim 1 wherein said water is present in said
composition in an amount in the range of from about 35% to about
100% by weight of cement therein.
7. A well cement composition comprising a hydraulic cement,
sufficient water to form a pumpable slurry and a fluid loss control
polymer additive that comprises 77.9 weight % of the calcium salt
of 2-acrylamido-2-methyl propane sulfonic acid, 8 weight % of the
calcium salt of maleic acid, 11 weight % of N-vinyl caprolactam, 3
weight % of 4-hydroxybutyl vinyl ether and 0.1 weight % of
methylene bisacrylamide.
8. The composition of claim 7 wherein said fluid loss control
polymer additive is present in said cement composition in an amount
in the range of from about 0.1% to about 2% by weight of cement in
said composition.
9. The composition of claim 7 wherein said hydraulic cement is
selected from the group consisting of Portland cements, pozzolana
cements, gypsum cements, aluminous cements and silica cements.
10. The composition of claim 7 wherein said hydraulic cement is
Portland cement.
11. The composition of claim 7 wherein said water is selected from
the group consisting of fresh water and salt water.
12. The composition of claim 7 wherein said water is present in an
amount in the range of from about 35% to about 100% by weight of
cement of said composition.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to well cementing methods and
compositions.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in the
construction and repair of oil and gas wells. For example,
hydraulic cement compositions are used in primary cementing
operations whereby strings of pipe such as casing or liners are
cemented in well bores. In performing primary cementing, a
hydraulic cement composition is pumped into the annular space
between the walls of a well bore and the exterior surfaces of a
pipe string disposed therein. The cement composition is permitted
to set in the annular space thereby forming an annular sheath of
hardened substantially impermeable cement therein. The cement
sheath physically supports and positions the pipe string in the
well bore and bonds the exterior surfaces of the pipe string to the
walls of the well bore whereby the undesirable migration of fluids
between zones or formations penetrated by the well bore is
prevented. Hydraulic cement compositions are also commonly used to
plug lost circulation and other undesirable fluid inflow and
outflow zones in wells, to plug cracks or holes in pipe strings
cemented therein and to accomplish other required remedial well
operations.
In order for such well cementing operations to be successful, the
cement compositions utilized must include a fluid loss control
additive to reduce the loss of fluid, i.e., water, from the cement
compositions when they contact permeable subterranean formations or
zones. Excessive fluid loss causes a cement composition to be
prematurely dehydrated which limits the amount of cement
composition that can be pumped, decreases the compressive strength
of the cement composition and prevents or reduces bond strength
between the set cement composition and a subterranean zone, the
walls of pipe and/or the walls of the well bore.
Heretofore polymers and copolymers have been utilized as fluid loss
control additives for well cements. A particularly suitable
copolymer which has been utilized as a cement composition fluid
loss control additive is a copolymer of 2-acrylamido-2-methyl
propane sulfonic acid and N,N-dimethylacrylamide having mole ratios
of 2-acrylamido-2-methyl propane sulfonic acid to
N,N-dimethylacrylamide of between 1:4 and 4:1 respectively, and
having an average molecular weight of between about 75,000 and
3,000,000. While the above described copolymer well cement fluid
loss control additive has achieved commercial success, there is a
continuing need for improved polymer fluid loss control additives
which achieve better fluid loss control in well cement compositions
particularly at high temperatures.
SUMMARY OF THE INVENTION
The present invention provides well cementing methods and
compositions which include improved fluid loss control additives
that reduce the loss of water from cement compositions including at
high temperatures, e.g. 230.degree. F. The fluid loss control
additives comprise water soluble polymers that meet the need
described above and overcome the deficiencies of the prior art. The
water soluble fluid loss control polymer additives which are useful
in accordance with this invention comprise the following monomers:
a) 5 to 93 weight % of monomers of the formula (Ia) or (Ib) or
both
##STR00001## wherein R' is hydrogen or C.sub.1 C.sub.5 alkyl,
R.sup.2 is C.sub.1 C.sub.20 alkylene, carboxy C.sub.1-C.sub.20
alkylene, carboamido C.sub.1 C.sub.20 alkylene or phenylene, M is
hydrogen, ammonium or a metal cation in the oxidation state +I, +II
or +III and x is 1 to 3; b) 1 to 50 weight % of monomers of the
formula (IIa) or (IIb) or both
##STR00002## wherein R.sup.3 and R.sup.4 are
--COO.sup.-(M.sup.x+).sub.1/x or
##STR00003## R.sup.5 is --COO.sup.-(M.sup.x+).sub.1/x, M is
hydrogen, ammonium or a metal cation in the oxidation state +I,
+III or +III and x is 1 to 3; c) 5 to 93 weight % of a monomer of
the formula (III)
##STR00004## wherein R.sup.6 is hydrogen or C.sub.1-C.sub.5 alkyl,
R.sup.7 is hydrogen, C.sub.1 C.sub.10 alkyl or
--(CH.sub.2).sub.y--, R.sup.8 is hydrogen, C.sub.1 C.sub.10 alkyl
or --(CH.sub.2).sub.y--, and y is 3 to 7; and d) 1 to 25 weight %
of monomers of the formulas (IVc) or (IVa) and (IVc) or (IVb) and
(IVc) or (IVa), (IVb) and (IVc).
##STR00005## wherein R.sup.6 is hydrogen or C.sub.1 C.sub.5 alkyl,
R.sup.9 is hydrogen or C.sub.1 C.sub.5 alkyl, R.sup.10 is C.sub.1
C.sub.10 alkyl, C.sub.1 C.sub.10 aminoalkyl, C.sub.1 C.sub.20
hydroxyalkyl, C.sub.1 C.sub.4 alkyl or hydroxyl terminated mono- or
poly-C.sub.2 C.sub.3 alkylenoxy (with 1 to 400 alkylenoxy units),
C.sub.7 C.sub.20 alkylaryl, C.sub.7 C.sub.20 hydroxyalkylaryl,
C.sub.6 C.sub.10 aryl, C.sub.6 C.sub.10 hydroxyaryl, R.sup.11,
R.sup.12 and R.sup.13 are hydrogen or C.sub.1 C.sub.5 alkyl,
R.sup.14 is hydrogen, C.sub.1 C.sub.20 alkyl, C.sub.1 C.sub.10
aminoalkyl, C.sub.1 C.sub.20 hydroxyalkyl, C.sub.1 C.sub.4 alkyl or
hydroxyl terminated mono- or poly-C.sub.2 C.sub.3 alkylenoxy (with
1 to 400 alkylenoxy units), C.sub.7 C.sub.20 alkylaryl, C.sub.7
C.sub.20 hydroxyalkylaryl, C.sub.6 C.sub.10 aryl, C.sub.6 C.sub.10
hydroxyaryl or with hydroxyl substituted C.sub.1 C.sub.20
alkylensulfonic acids and their ammonium, alkali metal or alkaline
earth metal salts, R.sup.15 is
##STR00006## X is O, NH, and x is 1 to 6 wherein the monomers add
up to 100 weight %.
The methods of this invention for cementing a subterranean zone
penetrated by a well bore basically comprise the following steps. A
cement composition is prepared or provided comprising a hydraulic
cement, sufficient water to form a pumpable slurry and a fluid loss
control polymer additive as described above. The composition is
placed into the subterranean zone to be cemented and then allowed
to set into an impermeable solid mass therein.
The cement compositions of this invention basically comprise a
hydraulic cement, sufficient water to form a pumpable slurry and a
fluid loss control polymer additive as described above.
A preferred fluid loss control polymer additive useful in this
invention is a polymer containing the calcium salt of
2-acrylamido-2-methyl propane sulfonic acid in an amount of about
77.9 weight %, the calcium salt of maleic acid in an amount of
about 8 weight %, N-vinyl caprolactam in an amount of about 11
weight %, 4-hydroxybutyl vinyl ether in an amount of about 3 weight
% and methylene bisacrylamide in an amount of about 0.1%. The
polymer additive has a molecular weight of about 250,000.
The objects, features and advantages of the present invention will
be readily apparent to those skilled in the art upon a reading of
the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The methods of the present invention for cementing a subterranean
zone penetrated by a well bore at temperatures up to and including
230.degree. F. and higher basically comprise the following steps. A
cement composition is prepared or provided comprising a hydraulic
cement, sufficient water to form a pumpable slurry and a fluid loss
control polymer additive. The cement composition is placed in the
zone to be cemented and thereafter the cement composition is
allowed to set into an impermeable solid mass therein. The
placement of the cement composition is usually accomplished by
pumping the cement composition through the well bore and into the
zone to be cemented.
The cement compositions of this invention basically comprise
hydraulic cement, sufficient water to form a pumpable slurry and a
fluid loss control polymer additive.
A variety of hydraulic cements can be utilized in accordance with
the present invention including, but not limited to, Portland
cements, pozzolana cements, gypsum cements, aluminous cements and
silica cements. Portland cements are generally preferred with the
types defined and described in API Specification For Materials And
Testing For Well Cements, API Specification 10B, 22.sup.nd Edition,
dated December, 1997 of the American Petroleum Institute being
particularly suitable. Preferred such API Portland cements include
classes A, B, C, G and H with API classes G and H being more
preferred.
The water in the cement compositions can be fresh water or salt
water. The term "salt water" includes unsaturated salt solutions
and saturated salt solutions including brines and seawater.
Generally, any water can be utilized so long as it does not
adversely affect components of the well cement composition. The
water is generally present in a cement composition of this
invention in an amount sufficient to form a pumpable slurry, i.e.,
in an amount in the range of from about 30% to about 120% by weight
of cement in the composition. The water is generally present in the
cement composition in an amount in the range of from about 35% to
about 100% by weight of hydraulic cement therein.
As mentioned above, the polymeric fluid loss control additives
useful in accordance with this invention are water soluble polymers
containing four different monomers, the principal monomer being an
olefinic sulfonic acid.
More specifically, the fluid loss control polymers contain: a) 5 to
93 weight % of monomers of the formula (Ia) or (Ib) or both
##STR00007## wherein R.sup.1 is hydrogen or C.sub.1 C.sub.5 alkyl,
R.sup.2 is C.sub.1 C.sub.20 alkylene, carboxy C.sub.1 C.sub.20
alkylene, carboamido C.sub.1 C.sub.20 alkylene or phenylene, M is
hydrogen, ammonium or a metal cation in the oxidation state +I, +II
or +III and x is 1 to 3; b) 1 to 50 weight % of monomers of the
formula (IIa) or (IIb) or both
##STR00008## wherein R.sup.3 and R.sup.4 are
--COO.sup.-(M.sup.x+).sub.1/x or
##STR00009## R.sup.5 is --COO.sup.-(M.sup.x+).sub.1/X, M is
hydrogen, ammonium or a metal cation in the oxidation state +I, +II
or +III and x is 1 to 3; c) 5 to 93 weight % of a monomer of the
formula (III)
##STR00010## wherein R.sup.6 is hydrogen or C.sub.1 C.sub.5 alkyl,
R.sup.7 and R.sup.8 are hydrogen, C.sub.1 C.sub.10 alkyl or
--(CH.sub.2).sub.y--, and y is 3 to 7; and d) 1 to 25 weight % of
monomers of the formulas (IVc) or (IVa) and (IVc) or (IVb) and
(IVc) or (IVa), (IVb) and (IVc).
##STR00011## wherein R.sup.6 is hydrogen or C.sub.1 C.sub.5 alkyl,
R.sup.9 is hydrogen or C.sub.1 C.sub.5 alkyl, R.sup.10 is C.sub.1
C.sub.10 alkyl, C.sub.1 C.sub.10 aminoalkyl, C.sub.1 C.sub.20
hydroxyalkyl, C.sub.1 C.sub.4 alkyl or hydroxyl terminated mono- or
poly-C.sub.2 C.sub.3 alkylenoxy (with 1 to 400 alkylenoxy units),
C.sub.7 C.sub.20 alkylaryl, C.sub.7 C.sub.20 hydroxyalkylaryl,
C.sub.6 C.sub.10 aryl, C.sub.6 C.sub.10 hydroxyaryl, R.sup.11,
R.sup.12 and R.sup.13 are hydrogen or C.sub.1 C.sub.5 alkyl,
R.sup.14 is hydrogen, C.sub.1 C.sub.20 alkyl, C.sub.1 C.sub.10
aminoalkyl, C.sub.1 C.sub.20 hydroxyalkyl, C.sub.1 C.sub.4 alkyl or
hydroxyl terminated mono- or poly-C.sub.2 C.sub.3 alkylenoxy (with
1 to 400 alkylenoxy units), C.sub.7 C.sub.20 alkylaryl, C.sub.7
C.sub.20 hydroxyalkylaryl, C.sub.6 C.sub.10 aryl, C.sub.6 C.sub.10
hydroxyaryl or with hydroxyl substituted C.sub.1 C.sub.20
alkylensulfonic acids and their ammonium, alkali metal or alkaline
earth metal salts, R.sup.15 is
##STR00012## X is O, NH, and x is 1 to 6 wherein the monomers add
up to 100 weight %.
R.sup.1 and R.sup.2 of the monomers of the formulas (Ia) and (Ib)
of the fluid loss control polymers of this invention are preferably
hydrogen and --CO--NH--C(CH.sub.3).sub.2--CH--, respectively, and M
in the monomers of the formulas (Ia), (Ib), (IIa) and (IIb) are
preferably metal cations wherein the +I metal cations are alkali
metal ions, most preferably sodium or potassium ions, the +II metal
cations are alkaline earth metal ions, most preferably calcium or
magnesium ions and the +III metal cations are aluminum or iron
ions.
In the monomer of the formula (III) y is preferably 3 to 5, and in
the monomer of the formula (IV), R.sup.9 is preferably hydrogen,
R.sup.10 is preferably --CH.sub.2--, X is preferably --NH--, and x
is preferably 1.
The fluid loss control polymers preferably contain 40 to 83 weight
% of the monomers of the formulas (Ia), (Ib) or both, 5 to 48
weight % of the monomers of the formulas (IIa), (IIb) or both, 10
to 53 weight % of the monomer of the formula (III) and 1 to 10
weight % of the monomer of the formula IV.
A fluid loss control polymer of this invention preferably has a
molecular weight in the range of from 10,000 to 3,000,000 grams per
mole, more preferably in the range of from 100,000 to 1,000,000
grams per mole.
A preferred fluid loss control polymer of this invention comprises
of 77.9 weight % of the calcium salt of 2-acrylamido-2-methyl
propane sulfonic acid (I), 8 weight % of the calcium salt of maleic
acid (II), 11 weight % of N-vinyl caprolactam (III), 3 weight % of
4-hydroxybutyl vinyl ether (IV) and 0.1 weight % of methylene
bisacrylamide (IV).
The fluid loss control polymer additives of this invention can be
prepared using known polymerization techniques.
A fluid loss control polymer additive as described above is
included in a cement composition of this invention in an amount in
the range of from about 0.1% to about 2% by weight of cement in the
composition. As mentioned above, the fluid loss control polymers of
this invention function to prevent fluid loss at temperatures up to
and including 230.degree. F. and higher.
As will be understood by those skilled in the art, a variety of
other well cement composition additives known to those skilled in
the art can be included in the cement compositions of this
invention. Such additives include, but are not limited to, set
retarding additives, set accelerating additives, dispersing agents,
lightweight additives and the like.
A preferred method of cementing a subterranean zone penetrated by a
well bore of this invention comprises the steps of: (a) preparing
or providing a cement composition comprising a hydraulic cement,
sufficient water to form a pumpable slurry and a fluid loss control
polymer additive comprising 77.9 weight % of the calcium salt of
2-acrylamido-2-methyl propane sulfonic acid, 8 weight % of the
calcium salt of maleic acid, 11 weight % of N-vinyl caprolactam, 3
weight % of 4-hydroxybutyl vinyl ether and 0.1 weight % of
methylene bisacrylamide; (b) placing the composition in the zone to
be cemented; and (c) allowing the cement composition to set into an
impermeable solid mass therein.
A more preferred method of cementing a subterranean zone penetrated
by a well bore comprises the steps of: (a) preparing or providing a
cement composition comprising Portland cement, sufficient water to
form a pumpable slurry and a fluid loss control polymer additive
comprising 77.9 weight % of the calcium salt of
2-acrylamido-2-methyl propane sulfonic acid, 8 weight % of the
calcium salt of maleic acid, 11 weight % of N-vinyl caprolactam, 3
weight % of 4-hydroxybutyl vinyl ether and 0.1 weight % of
methylene bisacrylamide present in the cement composition in an
amount in the range of from about 0.1% to about 2% by weight of
hydraulic cement therein; (b) placing the composition in the zone
to be cemented; and (c) allowing the cement composition to set into
an impermeable solid mass therein.
A preferred well cement composition of this invention comprises a
hydraulic cement, sufficient water to form a pumpable slurry and a
fluid loss control polymer additive comprising 77.9 weight % of the
calcium salt of 2-acrylamido-2-methyl propane sulfonic acid, 8
weight % of the calcium salt of maleic acid, 11 weight % of N-vinyl
caprolactam, 3 weight % of 4-hydroxybutyl vinyl ether and 0.1
weight % of methylene bisacrylamide.
A more preferred well cement composition comprises Portland cement,
sufficient water to form a pumpable slurry and a fluid loss control
polymer additive comprising 77.9 weight % of the calcium salt of
2-acrylamido-2-methyl propane sulfonic acid, 8 weight % of the
calcium salt of maleic acid, 11 weight % of N-vinyl caprolactam, 3
weight % of 4-hydroxybutyl vinyl ether and 0.1% of methylene
bisacrylamide present in the well cement composition in an amount
in the range of from about 0.1% to about 2% by weight of cement in
the composition.
In order to further illustrate the compositions of this invention,
the following examples are given:
EXAMPLE 1
A cement composition was prepared comprising Class H cement,
deionized water in an amount of 5.08 gal. per sack of cement,
silica flour in an amount of 35% by weight of cement and a modified
lignosulfonate set retarder in an amount of 0.5% by weight of
cement. To a first sample of the cement composition a prior art
fluid loss control additive was added, and to a second sample of
the cement composition a fluid loss control polymer additive of
this invention was added. The resulting first and second samples of
the cement composition were then tested for fluid loss at
230.degree. F. in accordance with the API Specification For
Materials and Testing For Well Cements. The results of these tests
are given in Table I below.
TABLE-US-00001 TABLE I Cement Composition Fluid Loss Silica Set
Fluid Loss Flour, Retarder, Fluid Control Water, % by wt. % by wt.
Temp., Loss, Additive gal/sk of Cement of Cement .degree. F. cc/min
Prior Art.sup.1 5.08 35 0.5 230 56 Present Invention 5.08 35 0.5
230 44 .sup.1Copolymer of N,N-dimethylacrylamide and 2-acrylamido-2
methyl propane sulfonic acid. (See U.S. Pat. No. 4,444,269)
From Table I, it can be seen that the fluid loss control additive
of this invention provided less fluid loss than the prior art fluid
loss control additive.
EXAMPLE 2
The procedure set forth in Example 1 was repeated except that the
cement composition comprised Class H cement, water in an amount of
4.8 gal. per sack of cement, crystalline silica in an amount of 35%
by weight of cement and a set retarder comprising a copolymer of
2-acrylamido-2 methyl propane sulfonic acid and acrylic acid in an
amount of 1% by weight of cement. To a first sample of the cement
composition, a prior art fluid loss control additive was added, and
to a second sample of the cement composition a fluid loss control
polymer additive of this invention was added. The resulting first
and second samples of the cement composition were then tested for
fluid loss at 150.degree. F. The results of these tests are given
in Table I below.
TABLE-US-00002 TABLE II Crystalline Set Fluid Loss Silica,
Retarder, Fluid Control Water, % by wt. % by wt. Temp., Loss,
Additive gal/sk of Cement of Cement .degree. F. cc/min Prior
Art.sup.1 4.8 35 1 150 50 Present Invention 4.8 35 1 150 34
.sup.1Copolymer of N,N-dimethylacrylamide and 2-acrylamido-2 methyl
propane sulfonic acid.
From Table II, it can again be seen that the fluid loss control
additive of this invention provided less fluid loss than the prior
art fluid loss control additive.
Thus, the present invention is well adapted to carry out the
objects and attain the benefits and advantages mentioned as well as
those which are inherent therein. While numerous changes can be
made by those skilled in the art, such changes are encompassed
within the spirit of this invention as defined by the appended
claims.
* * * * *